The present invention generally relates to electronic combination locks and, more particularly, electronic combination locks requiring a small amount of electrical power to be placed in an unlockable condition and then requiring the user to manually retract the lock-bolt after being placed in the unlockable condition.
One particular electronic combination lock is shown and described in U.S. Pat. No. 5,881,589 (the ""589 patent), the disclosure of which is hereby fully incorporated by reference herein. Additional related locks are disclosed in U.S. Pat. Nos. 5,061,923 and 5,487,290, assigned to the assignee of the present invention and the disclosures of which are also fully incorporated by reference herein. The present invention improves upon these types of locks, however, the principles of the present invention are applicable to other electronic combination locks as well. The lock are described in the ""589 patent and other similar locks essentially require the user to input a proper combination electronically. For example, this input can occur through rotating a combination dial or pressing the appropriate series of numbers on a keypad associated with the lock. The lock may be battery operated or powered by other sources. These locks may also have an electricity generating device, such as a stepper motor, for supplying a small amount of power for the combination input device as well as subsequent electrical functions. These subsequent electrical functions include the actuation of a small electrical actuator, such as a small stepper motor, to allow the lock to be placed into an unlockable condition. In the ""589 patent, the stepper motor rotates a small gear and places the gear in an engageable position for meshing with another manually operable gear connected with the dial of the electronic combination lock. The gear connected to the stepper motor is further connected to one or more gears which ultimately connect with the lock-bolt. Other mechanical systems have also been used in place of a gear system, such as systems using levers, slides, etc., facilitating an operable connection between the manually rotatable drive gear or cam and the lock-bolt.
These general types of combination locks are used in high security applications and are in constant need of improvement to counteract the efforts of various unauthorized individuals from compromising the lock or, in other words, withdrawing the lock-bolt without entering the proper combination. One potential problem involves the rotation of the gear connected with the motor through some method that does not involve entering the proper combination into the lock. Once rotated into the engageable position through manual means or other means, the manually operable drive gear may be turned by the user to withdraw the lock-bolt. For reasons such as these, and to improve the overall security of electronic combination locks of this variety, it would be desirable to provide an electronic combination lock that provides further preventive measures against unauthorized entry through the lock.
The present invention therefore provides various improvements in the security of electronic combination locks. Generally, an electronic combination lock constructed in accordance with the invention includes an electronic combination input device, a lock-bolt mounted for movement between locked and unlocked positions, a rotatable first engagement element having disengaged and engageable positions, and a first electric actuator electrically connectable with the electronic combination input device and having a rotatable output for rotating the first engagement element to the engageable position thereof in response to a proper combination input into the electronic combination input device. A manually operated and rotatable second engagement element can be engaged with the first engagement element when the first electric actuator moves the first engagement element into its engageable position. A lock-bolt drive mechanism is operatively coupled between the lock-bolt and the first engagement element. Therefore, during normal operation, when the first engagement element is moved by the first electric actuator into its engageable position, the second engagement element may be rotated by the user to activate the lock-bolt drive mechanism and thereby move the lock-bolt to its unlocked position. In accordance with the improvements provided by the preferred embodiment of this invention, a second electric actuator having a movable output is also operatively coupled to the first engagement element and prevents the first engagement element from rotating until the proper combination is input by a user. Preferably, when the user inputs the proper combination, electric current is sent to both the first and second electric actuators such that these actuators are activated at least nearly simultaneously or in a manner allowing the second electric actuator to allow rotation of the first engagement element and then allow the first electric actuator to rotate the first engagement element into its engageable position.
The second electric actuator preferably prevents rotation of the first engagement element except upon entry of a proper combination. This second electric actuator is preferably an electric solenoid device having a movable member or portion which is operatively coupled to the first engagement element and may be electrically activated in at least one direction between the locked and unlocked positions. In one embodiment, a movable pin is normally spring-biased into a locked position within a hole or recess in the first engagement element and, under the effects of electric current, is driven to an unlocked position when the solenoid device is activated. The movable member may include a flat, resilient plate connected to a movable pin or portion of the solenoid device and disposed between the solenoid device and the first engagement element. Also, for retrofitting purposes, the first and second electric actuators are preferably mounted to a common support structure. This allows easy replacement of the electric motor, for example, used in a lock constructed according to the ""589 patent, with the retrofittable assembly of the present invention.
While the use of a second electric actuator to prevent unauthorized rotation of the first engagement element is preferable, other means of preventing manual rotation of the first engagement element may be used as well. As one example, the first electric actuator could be substituted with a two-step actuator which must move both linearly and in a rotating manner to engage the second engagement element. Other manners of ensuring that the first engagement element cannot be moved into engagement with the second engagement element through manual effort without entering a proper combination may be utilized by those of ordinary skill as well while still retaining the inventive concepts expressed herein.
The present invention further contemplates a method of operating an electronic combination lock having a lock-bolt movable between locked and unlocked positions and a first engagement element movable into and out of an engaged position with respect to a second engagement element by a first electric actuator as generally discussed above. The method includes placing the lock-bolt into its locked position, preventing the first engagement element from being manually moved into engagement with the second engagement element to prevent movement of the lock-bolt to the unlocked position by the lock-bolt drive mechanism, and entering a proper combination into the electronic combination input device. Once the proper combination has been input by a user, a first pulse of electricity is sent to the electric actuator and it activates in response. A second pulse of electricity is sent to a second electric actuator or to another means to stop preventing the first engagement element from being manually moved into engagement with the second engagement element. This allows or causes the electric actuator to move the first engagement element into engagement with the second engagement element. In this manner, the lock-bolt may then be moved to the unlocked position using the lock-bolt drive mechanism and, for example, a manually rotatable dial on the outside of the lock. Other drives include knobs or levers, and in some cases, motorized drives for retracting the lock-bolt.